This document provides an overview of motherboard components and layout. It describes the main components of a motherboard including the CPU socket, memory slots, I/O ports, BIOS, disk connectors, and expansion bus slots. It explains common bus standards like PCI, AGP, and PCIe. It also defines different motherboard form factors such as ATX, NLX, and BTX and describes their features and advantages. Finally, it provides a detailed description of the functions and types of computer buses that connect components within a computer system.

1. Module 1/unit 2
By Kenneth Ayebazibwe
256774185458 / 0702555890
kynaye@gmail.com

2. objectives
– On completion of this unit, you will be able to;
– Identify and describe the main components of a
motherboard
• CPU Sockets and chipsets
• System clock
• Memory Slots
• I/O ports
• ROM BIOS
• Disk connectors
-Identify expansion bus slots and cards
-Describe the capabilities of PCI, AGP and PCIe bus standards
-Describe ATX,NLX,BTX and proprietary motherboard form factors
-Identify the use and connectors for a PC Power Supply Unit(PSU)

3. Mother board Layout

4. Mother board Layout
• In personal computers, a motherboard (sometimes
alternatively known as the mainboard, system board,
planar board or, on logic board[) is the central printed
circuit board in many modern computers and holds many
of the crucial components of the system, providing
connectors for other peripherals.
• Motherboard specifically refers to a printed circuit board
with expansion capability. The term mainboard is applied
to devices with a single board and no additional
expansions or capability. In modern terms this would
include controlling boards in televisions, washing
machines and other embedded systems.

5. Motherboard
components

6. System clock
• In computers, sequence is everything. The system
clock synchronizes the tasks in a computer, like
loading data before manipulating it, etc. The system
clock is a circuit that emits a continuous stream of
precise high and low pulses that are all exactly the
same length. One clock cycle is the time that passes
from the start of one high pulse, until the start of
the next. If several events are supposed to happen
in one clock cycle, the cycle is subdivided by
inserting a circuit with a known delay in it, thus
providing more highs and more lows.

7. Computer Bus Architecture Types
• Computers comprises of many internal components and
in order for these components to communicate with each
other, a ‘bus’ is used for that purpose.
• A bus is a common pathway through which information
is flows from one component to another. This pathway is
used for communication and can be established between
two or more computer components. We are going to
review computer bus architectures that are used in
computers.
• The functions of buses can be summarized as below:

8. Functions Of Buses
• Data sharing - the expansion bus must be able to transfer data
between the computer and the peripherals connected to it.
• The data is transferred in parallel, which allows the exchange of 1, 2, 4
or even 8 bytes of data at a time. (A byte is a group of 8 bits). Buses are
classified depending on how many bits they can move at the same
time, which means that we have 8-bit, 16-bit or even 32-bit buses.
• Addressing - A bus has address lines, which match those of the
processor. This allows data to be sent to or from specific memory
locations.
• Power - A bus supplies power to various peripherals that are
connected to it.
• Timing - The bus provides a system clock signal to synchronize the
peripherals attached to it with the rest of the system.

9. Bus Terminologies
• Computers can be viewed to be having just two types of
buses:
System bus:- The bus that connects the CPU to main
memory on the motherboard. The system bus is also
called the front-side bus, memory bus, local bus, or host
bus.
A number of I/O Buses, (Acronym for input/output),
connecting various peripheral devices to the CPU -these
are connected to the system bus via a ‘bridge’
implemented in the processors chipset. Other names for
the I/O bus include “expansion bus", "external bus” or
“host bus”.

10. EXPANSION BUS TYPES
• These are some of the common expansion bus types that
have ever been used in computers:
– ISA - Industry Standard Architecture
– EISA - Extended Industry Standard Architecture
– MCA - Micro Channel Architecture
– VESA - Video Electronics Standards Association
– PCI - Peripheral Component Interconnect
– PCMCIA - Personal Computer Memory Card Industry
Association (Also called PC bus)
– AGP - Accelerated Graphics Port
– SCSI - Small Computer Systems Interface.

11. What exactly is Motherboard Form
Factor?
• Motherboards have different form factors. A
form factor is simply the physical size and layout
of the motherboard and its components. Several
form factors and their features are described
below.

12. • Advanced Technology (AT) and Baby AT
• Advanced Technology (AT) and baby AT form factors were the most popular types of
motherboards on the market. The main difference between the two is the width of the
motherboards, themselves. The AT motherboard is 12 inches wide by 13 inches long.
The baby AT is 9 inches wide by 10 inches long. See Figure 2.1 for the baby AT and
its components.
• The AT and baby AT form factors have the processor and memory socket locations
toward the front of the motherboard. Very long expansion cards were designed to
extend over them, which made removing the processor difficult. One had to take the
expansion cards out first to remove the processor or to get to the memory. It is
important to note that an AT power supply gives an output of 12V and 5V to the
motherboard. Additional regulators are needed on the motherboard if 3.3V cards
(peripheral component interface, or PCI) or processors are used.
• This design was acceptable when clearance and cooling were not issues. With the
advent of faster Pentium-class processors, which required more cooling and memory
sockets that extended off the motherboards, a better motherboard design was needed.

13. Advanced Technology (AT) and
Baby AT

14. LPX
• Western Digital introduced the Low Profile Extensions (LPX)
motherboard form factor. This form factor was developed to
meet the need for a slimmer desktop. This goal was
accomplished based on the implementation of a riser card that
extended from the motherboard and allowed expansion cards
to be installed parallel to the motherboard.
NLX
• As the need for more expansion slots and easier access to
components increased, the LPX form factor was redesigned
by Intel and named the NLX (InteLex) form factor. The NLX
form factor moved the riser card from the center of the
motherboard to the outside edge.

15. LPX
NLX

16. ATX
• The ATX form factor was developed to solve the
problems associated with the baby AT form factor
design. This new design had many advantages that
affected not only the motherboard, but the system
unit and power supply, as well. The dimensions of
the ATX form factor are 12 inches wide by 9.6
inches long. A mini ATX is typically 11.2 inches
wide by 8.2 inches long.

17. Advantages of ATX form factor.
Integrated I/O port connection.
• Baby AT motherboards have cables connecting them to the physical serial
and parallel ports mounted on the system unit. With the ATX form factor,
this connection is integrated into the motherboard. The ATX form factor
uses a 20-pin plastic power supply connector. This is called a keyed
connector, and it can be plugged into the motherboard in one direction only.
Integrated PS/2 mouse connector.
• ATX motherboards have PS/2 mouse ports integrated into the motherboard.
Most baby AT motherboards do not have a PS/2 mouse port. Older-style AT
motherboards required a serial mouse.
Easier access to components.
• The ATX motherboard was designed with functionality and accessibility in
mind. It provides much easier access to components than the baby AT form
factor and offers more room in general for additional components.

18. Improved power supply connection.
• The new ATX form factor incorporated a single 20-pin connector in place of
the pair of 6-pin connectors used on the baby AT motherboard.
Support for 3.3V.
• The ATX motherboard supports 3.3V power from the ATX power supply.
This voltage is used by most new processors.
'Soft switch' power support.
• The ATX power supply uses a signal from the motherboard to turn itself off.
This feature enables you to use the power management utilities offered with
newer operating systems to shut down a computer, as opposed to physically
turning it off with the power button.
Better airflow.
• With the ATX form factor, the processor is moved closer to the power
supply, providing it with better air circulation and cooling. For proper air
circulation, it is also important to replace any slot covers on the back of a
computer that may be missing as a result of removed expansion cards.

19. Motherboard component
• CPU Socket : This section is the place laid a processor even with the
many small holes that are used to place a pin processor.
• RAM Slots : Places to install the memory module (RAM). For a
modern motherboard, usually there are 4 slots DDR2 PC 6400 with a
capacity of up to 8GB and support for dual-channel configuration.
• Power Port : Old type use 20 +4 pin, while new types have been using
24 +4 pin. Through this port all the power needed by the system
supplied through the power supply.
• Serial ATA Port : The new type motherboard using this port. Usually
there are 4 to 8. It is used for hard disk drives where using SATA
interface. Cable that is used is usually smaller than the IDE cable.
SATA technology is growing rapidly, at this time is to reach the next
generation of SATA-2 with data transfer speeds up to 3Gb/s.

20. • IDE Port : It is only found in old type of motherboard. That is used to install
the hard disk drive and optical drives, it has an large size of the cable width.
• Chip-set : A chip that regulates the data traffic on the system. There are 2
types of chip set with a different function with each other. North-bridge chip-
set is located between the processor and RAM slots. This chip-set works so
RAM and processor modules can work together (set of traffic data between
the CPU and RAM). South-brigde chip-set is located on the bottom. Either
the bottom of the processor or under the slot for graphics cards. Chip-set
handle this work flow of traffic data from the graphics card, hard disk and
other motherboard peripherals.
• AGP / PCI Express Slot : Used to install the graphics card. AGP slot is
rarely found in the new type, because the resulting bandwidth is not sufficient
for the needs of graphics at this time. Now, almost all motherboards use the
PCI Express slot, with a larger bandwidth. In fact, there are motherboards
that have up to 4 PCI Express slots.

21. • PCI (Peripheral Component Interconnect) : Is
the place to put additional cards such as sound card,
LAN card, TV tuner, and others. It is working at 33
Mhz frequency.
• BIOS (Basic Input Output System) : Form of
software that is embedded in the motherboard
where the energy supplied from the motherboard
battery. All initial configuration of the hardware
that is installed can be accessed and changed
through the BIOS.

22. Review Questions
Motherboards
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